The major objectives are to continue research on prolactin, placental lactogens and their receptors. A prolactin-dependent rat lymphoma cell line, which has been developed, is proving to be of considerable value as an assay and also as a tool to examine the mechanism of action of prolactin. The purification of prolactin and growth hormone receptors continues. Attempts are being made to generate monoclonal antibodies to the partially purified receptors. Placental lactogens from rat, sheep and cow have been purified and regulatory factors influencing their secretion are being examined. The identification and significance of novel brain and pituitary growth factors will be explored. Studies on neuroendocrine factors and their influence on prolactin secretion will be examined.